Dyeing of synthetic linear polyamide fibers



Patented Nov. 5, 1940 UNITED STATES PATENT OFFICE DYEING OF SYNTHETIC LINEAR POLYAIHIDE FIBERS No Drawing. Application September 12, 1939, Serial No. 294,418

6 Claims.

This invention relates to the dyeing of synthetic linear polyamide fibers and to the treatment of such dyed material to effect a leveling out or equalization of the color between pieces of fabrics which have been dyed in different shades or strengths.

In copending U. S. application to Carothers et al., Serial No. 289,909, filed August 12, 1939, the dyeing of the new synthetic fiber-forming linear polyamides which are more particularly described in U. S. Patents 2,071,250, 2,071,253, 2,130,523 and 2,130,948 and in British specification 495,790 with the water insoluble dyestuffs of the cellulose acetate class is described. It was found that the water insoluble dyes which had previously been found suitable for use in dyeing cellulose acetate dye the new fiber-forming linear polyamidcs evenly and in strong shades.

These new polyamide fibers because of their good elasticity and wearing qualities have been found to be particularly suitable for the manufacture of stockings as more particularly described in U. S. Patent 2,157,116.

In the manufacture of ladies stockings where the shades in which they are dyed vary from season to season it is now the practice to strip the color from the left-over stock of stockings and to re-dye them in the new seasonal shades. The

colors in which ladies stockings are usually dyed are generally prepared by mixing several colors. The colors of the cellulose acetate class which are now employed in the'dyeing of the new polyamide fibers are of various types such as azo colors, anthraquinone compounds, etc., and since these colors which vary widely in chemical composition are not all removed to the same degree by any one stripping agent, difliculty is experienced in attempting to re-dye stockings in uniform shades where all of the stockings which are to be re-dyed in a single dye bath have not been entirely stripped of color or vary in shade after the stripping operation.

It is therefore an object of this invention to provide a process whereby the new polyamide fibers which are dyed in different shades or strengths with water insoluble cellulose acetate dyes may be treated to effect the leveling out or equalization of the colors on such fibers. It is a further object of the invention to provide a method whereby stockings comprising the new.

polyamide fibers which have been dyed in varying shades or strengths with water insoluble dyestuffs of the cellulose acetate class may be converted to the same shade to facilitate re-dyeing or may be stripped'uniformly of the dye already on .the fiber-so that they may be re-dyed from a single dye bath in level and uniform shades.

I have found that when stockings made from the new polyamide fibers are dyed with water insoluble cellulose acetate dyes as more particularly described in copending application 289,909, the colors can be leveled, out between stockings of widely different shades by heating them together in an aqueous solution of a dispersing agent at temperatures of from 180 F. to 200 F. 10

Although the water insoluble cellulose acetate colors which are employed for the dyeing of the new polyamides are in general fast to washing under conditions normally employed in washing silks and artificial silks, I have found that a rapid exchange of color between pieces of this new fiber dyed in different shades or strengths can be effected under the conditions above mentioned. By leveling out the colors on a large' number of variously dyed stockings, the re-dyeing of such stockings from season to season is greatly facilitated for inmany cases the dye already on the stockings may be utilized as a component of the new color. In cases where the out-moded shades are lighter in color than the new shade desired it is only necessary to level out the dyes between batches of stockings of varied shades by heating them with the dispersing agent in aqueous solution and then build up the color on the fiber by adding the necessary dyes directly to the leveling bath since in the leveling operation the darker shades are made lighter while the lighter colored stockings become darker. It is possible to re-dye even the darker stockings in a lighter shade without actual loss of dyestuff, providing the new shade in which the stockings are to be dyed is not lighter than the average shade to which all of the stockings are brought in the leveling bath. This makes the re-dyeing of the stockings of the new polyamide fiber much more economical than where the dye must be stripped K completely from the fiber before re-dyeing for all of the original dye is again employed and it is not necessary to re-work stockings of diflferent color separately. 45

Where the new shade is fighter than the average shade of the mass of stockings being worked part or all of the color may be stripped from the fiber. However, due to different fastness of the various components of the dye on the fiber it is difficult to remove all of the color by a single stripping operation. Part of the color may however, be stripped and the remaining color equalized over the batch of stockings by this leveling operation, thereby permitting a re-dyeing of all of the stockings in the same level shade although the stockings may originally have been dyed in a variety of shades or strengths which do not strip down to the same shade in the stripping bath.

5 The leveling may be efiected either before or after the stripping operation for if the colors have been equalized prior to stripping they are all reduced to the same color during the stripping operation even though one or more of the color components making up the dyestuff is not entirely removed.

This leveling process may also be used in leveling out the color on polyamide fabrics which have been dyed unevenly due to the use of too low temperature, too short a time or due to mechanical difficulties that may be experienced in the dyeing of fiber from time to time.

The dispersing agents which may be employed in the leveling operation may be any of those normally employed in the dyeing of cellulose acetate silk with colloidally dispersed water insoluble colors, such as soaps, Turkey red oil, the higher molecular weight alkyl sulfates and sulfonates, the octadecenyl aminoethane sulfonic acid, the

octadecenyl oxyethane sulfonic acid, the higher alkyl substituted aromatic sulfonic acids, the sul- -fonated naphthalene-formaldehyde condensation products, and the higher alkyl substituted bydroxy aromatic sulfonic acids, etc.

The leveling operation is preferably carried out at temperatures of from 180 to200 F. Within this range of temperature the exchange or leveling out of the color between stockings dyed in different shades or strengths is usually effected in from 30 to min.

The following examples are given to further illustrate the invention and the parts used are by weight.

Example 1 0 Three stockings made from a fiber-forming polyamide comprising polyhexamethylene adipamide each weighing 12 grams are dyed in different shades from dye baths comprising 300 grams 45 of water, 0.05 gram of a higher alcohol sodium sulfate made from alcohols containing from 12 to 18 carbon atoms, and the amounts of colloidally dispersed dyestufis given below:

Materials 1 2 3 Grams p-Nitro aniline ethyl hydroxy ethyl aniline 0.0285 0.045 0.105 l,4,5,8 tetra amino anthraqumone 0.0163 0.01 0.077

The dyeing is carried out for 1 hour at 180 F.

The three stockings are dyed in the following colors: light reddish-tan, medium yellow-brown,

medium blackish-brown.

The stockings dyed as above in shades corresponding to the current vogue for women's hosiery are treated together in a bath containing on the weight of the material 0.4% higher alcohol sodium sulfates made from alcohols containing 12 to 18 carbon atoms, 1% olive oil soap and v 0.25% soda ash or tri-sodium phosphate for 1 hour at 180-200 F. in a volume of 1:25. After this treatment the three stockings are substan- 0 tially the same shade and approximately equal to the shade obtained from an average of the color originally used (p-amino acetanilide p-'cresol- 0.066 g.; p-nitro-aniline ethyl hydroxy ethyl aniline --0.06 g.; 1,4,5,8-tetra amino anthraquinone0.037 g.).

If the shade resulting from this equalization treatment is lighter than the shade demanded for the next seasons requirements, additional dyestufis may be added to the same dye bath used for equalizing, to obtain the new shade. If the I shade resulting from this treatment is darker than the new requirement the composite shade can be stripped down to a light shade of blue by a treatment in a bath containing 5-10% of zinc formaldehyde sulfoxylate at a temperatum 10 of 200 F. for /g hour.

The advantage of equalizing the shade of the polyamide dyed with acetate colors before stripping may be illustrated as follows:

If the stockings, 1, 2 and 3 of Example 1, are 18 stripped separately by the treatment outlined above, it will be found that stocking 1 is almost white, stocking 3 is distinctly blue and and stocking 2 is intermediate in blueness between stockings l and 3.

The'explanation of this-lies in the fact that polyamide dyed with 1,4,5,8 tetra aminoanthraquinone is difiicult, ifnot impossible, to strip completely from this fiber. Inasmuch as different amounts of this dyestufi were used in the 25 dyeing of the three stockings, the shade resulting from the stripping process varied as indicated. The re-dyeing of these three stripped polyamide stockings of different blue shades to a uniform vogue shade, is diflicult on account of this varia- 39 tion in the blue base. These subsequent treatments may be illustrated by the following examples:

Since the leveling or exchange of the dye on this new fiber takes place between already dyed 35 pieces of goods, it will be obvious that by preliminary tests one can determine the amount of dye that must be added to a particular lot of variously colored stockings and the dye may be added to the leveling bath at the start of the level- 40 ing process, although ordinarily it will be preferred to level out the color and then' re-dye to the desired shade.

Example 2 Example 3 A stocking of the polyhexamethylene adipamide fiber weighing 12 grams, equalized in shade, stripped by means of zinc formaldehyde sulfoxylate and washed, is dyed in a bath containing 0.05 gram higher alcohol sodium sulfate made 60 from alcohols containing from 12 to 18 carbon atoms, 300 grams water, 0.06 gram 'p-amino acetanilide-m-cresol, 0.045 gram p-nitro aniline ethyl hydroxy ethyl aniline and 0.017 gram 1,4,5,8 tetra aminoanthraquinone and maintained 65 for 1 hour at 180 F. to obtain a stocking corresponding in shade to the original of stocking #2. It is assumed that approximately 60% of the color imparted by 1,4,5,8 tetra amino anthraquinone is removed during the stripping process. 70

Example 4 A skein of the polyamide fiber dyed with 0.17% of a colloid dispersion of the dye of U. S. Patent the dye of U. S. Patent 1,611,986 is heated as prescribed above with a white (undyed) skein 01' equal weight. The original dyed skein will be about its original depth of shade and the original undyed skein will be approximately the same depth of shade.

The advantage of this treatment is evident. It affords a method for-correcting errors in dyeing, for where the resulting shade is of greater intensity than desired it may be reduced in strength by the addition of .undyed material. The strong dyeing may be brought down in intensity to the desired shade without the necessity for stripping and redyeing.

Example 5 A piece of polyamide knit goods dyes with 0.15% p-nitro anilineaniline (an orange color) and a piece of similar knit goods dyes with 0.125% l-methyl amino-4-amino anthraquinone, (a violet color), when treated together as indicated above will balance in shade approximately equal to a combination dyeing'with a mixture containing the same amount of each color on knit goods equal in weight to the total weight of the two pieces.

This illustrates how goods of widely diflferent colors may be reduced to a common color easily and economically so they may be re-dyed in uniform shades without loss of the color originally used and without working up each individual color separately.

While in the specific examples given above only a limited number of colors have been used to illustrate the invention it is to be understood that this process may be used on the polyamide and related fibers which are dyed with water insoluble dyes of the cellulose acetate dye class that are applied to the fiber as colloidal dispersions, as more particularly described in copending application, Serial No. 289,909, filed August 12, 1939.

I claim:

1. The process for leveling out colors on synthetic linear polyamide fibers dyed with water insoluble dyes of the cellulose acetate dye class which comprises heating the dyed fibers in an aqueous solution of a dispersing agent at temperatures of from 180 to 200 F.

2. In the process for leveling out colors between goods made from synthetic linear polyamide fibers which have been dyed in diiferent shades with water insoluble cellulose acetate dyes, the step which comprises heating the polyamide goods of different shades in an aqueous solution of a dispersing agent at temperatures of from 180 to 200 F. until the shades and strengths of the colors are equalized.

3. In the process of redyeing stockings made i'rom' synthetic linear polyamide fibers which have been dyed previously in various shades with water insoluble cellulose acetate dyes, the step which comprises leveling out the colors between the stockings of varying shades by heating them together in an aqueous solution of a dispersing agent at 180 to 200 F. until the shades and strengths of the colors are equalized.

4. In the process from synthetic linear polyamide fibers which have been dyed previously in various shades with water insoluble cellulose acetate dyes, the steps which comprise leveling out the colors between the stockings of v ying shades by heating them together'inan aqueous solution 01' a dispersing agent at 180 to 200 F. until the shades and strengths of the colors are equalized and adding sumcient dye to the leveling bath to bring the ehtire mass of stockings to the desired uniform and 5: In the process of redyeing stockings made from synthetic linear polyamide fibers which have been dyed previously in various shades with water insoluble cellulose acetate dyes, the steps which comprise leveling out the colors between the stockings ofvarying shades by heating them together in an aqueous solution of a dispersing agent at 180 to 200 F. until the shades and strengths of the colors are equalized, then stripping off the readily removed color to a shade that is lighter. than the color to which the stockings are to be redyed whereby the stockings may all be dyed in uniform shades.

6. In the process of redyeing stockings made from synthetic linear polyamide fibers which have been dyed previously in various shades with water insoluble cellulose acetate dyes, the steps which comprise leveling out the colors between the stockings of varying shades by heating them together in an aqueous solution of a dispersing agent at 180 to 200 F. until the shades and strengths of the colors are equalized, then stripping off the readily removed color to a shade that is lighter than the color to which the stockings are to be redyed and redyeing the stockings which have thus been equalized in shade, to the PHILIP H. s'ro'rr desired color.

01' redyeing stockings made 

